An innovative system consisting of three different Chromium Carboxylate Acrylamide Polymer (CCAP) gels is being used in place of conventional cement squeezes in the Upper Spraberry formation located in West Texas. The application of the CCAP gel to shut off water production by abandoning the Upper Spraberry formation has resulted in increased oil production, lower workover costs and reduced lease operating expense (LOE) in the majority of the wells that have been treated to date.
A typical Spraberry Trend Area well consists of the Upper and Lower Spraberry and Dean formations. After fracture stimulation, the intervals are produced by beam pump. Reservoir characteristics and the completion configuration cause the Upper Spraberry formation to be more susceptible to water encroachment. Because the Upper Spraberry has low reservoir pressure, conventional squeeze cementing is difficult. The hydrostatic pressure resulting from a column of cement will further breakdown the formation requiring high cement volumes and/or multiple squeeze attempts in order to successfully shut off the interval. As an alternative to conventional cement squeezes, gel treatments with volumes between 700 and 1,000 barrels using three different gel systems are used to successfully shut off the Upper Spraberry formation.
One hundred eight wells have been treated to date. Many of the wells initially treated in 2003 are still benefiting from the gel treatment, maintaining oil production with lower water/oil ratios. Gel treatments have been successful in increasing or restoring oil production, and reducing operating expense and workover cost. Increases in gel treatment cost have been minimal over the years compared to that of cement. The gel treatments have proven to be a cost-effective, long-term alternative for conventional cement squeezes.